Plants synthesize starch in vegetative tissues during the daytime and degrade the starch at night to mobilize the resulting sugar in order to support the energy needs of the plant. Vegetative plant cells express a series of enzymes to initiate mobilization of transitory starch during the nighttime. Glucan Water Dikinase (“GWD”), which phosphorylates starch is one of these enzymes. GWD transcript levels were shown to undergo diel fluctuation (Smith et al. Plant Phys. Preview, Apr. 29, 2014). Increasing the starch content of biomass can increase the energy content (calories) in animal feed or improve glucose extraction from biomass for the production of ethanol or other biochemicals.
Different molecular methods exist for manipulating plant characteristics. Almost all of these methods rely on inserting new, synthetic or recombinant nucleic acids into a plant through the process of transformation. The nucleic acids thus inserted may encode a ribonucleic acid (RNA) or protein, which is expressed by the transformed plant and thereby changes the plant phenotype. In many cases, the nucleic acid may encode a heterologous protein or produce more of an endogenous protein. Similarly, the transformed nucleic acids may produce RNA that through a variety of mechanisms (such as RNA interference, antisense RNA, etc.) reduce expression of an endogenous gene thereby “silencing” the gene and production of its product. In all cases the nucleic acid inserted into the plant is expressed in a dominant manner; that is, its presence has a direct effect on the plant's characteristics. More recently, it has been demonstrated that by expressing nucleic acids that encode deoxyribonucleic acid (DNA) altering proteins (such as nucleases) in an organism, the organism's genome can be permanently altered, even after the inserted nucleic acids have been removed, and endogenous genes optimized. In this way it is possible to not only generate beneficial dominant traits, but also generate very specific, targeted mutations as the basis to create beneficial recessive traits, which would have been otherwise extremely difficult to find and develop for commercial applications. Currently there are no recessive traits created using nucleases in commercial use in row crops. Recessive traits generated using nucleases have been previously demonstrated in plants and plant cells, but never in fully developed, multicellular corn and sorghum plants, including hybrid corn and sorghum. Like dominant traits, recessive traits may have commercial value and may have specific commercial advantages (security and regulatory benefits in particular) over dominant traits. Such recessive traits will require new methods of propagating, tracking, and delivering the trait, particularly in hybrid crops.
One problem with dominant traits, particularly in hybrid and cross-pollinating crops, such as corn, is that they can be readily transferred to other lines of the same species. In regions of the world where farmers generate at least part of their own seed for planting, this affords the opportunity to breed a dominant trait into a farmer's existing lines, without paying the technology owner. The established trait business model currently requires seed and trait purchasers to pay the trait provider a royalty and licenses commonly limit use of the trait to a single planting and prohibit breeding. For many traits, monitoring unlicensed breeding is nearly impossible, and substantial unlicensed trait transfer (pirating) of traits occurs in some parts of the world. Depending on the trait, pirating or transferring the trait into a useable line without paying the technology owner can be an easy task and difficult for technology providers to detect. For example, pest resistance or agronomic traits, that do not require any other materials for their use, such as an herbicide resistance or specific fertilizer, are nearly impossible to detect if they have been transferred into a different line. Subsequent generations can be generated and tracked by a breeder using commercially available test strips or phenotypically if the trait confers an easily scorable phenotype. Because the trait is dominant, it may not need to be homozygous in the progeny for farmers to use it, and thereby enables easy continued breeding and use outside of the technology licensor's awareness.
In contrast to dominant traits, a recessive trait needs to be homozygous in the crop in order to phenotypically observed or easily scored. Simple test strips may not be available to track the molecular basis of the trait, and accurate breeding of a recessive trait made through the use of a nuclease may require at least polymerase chain reaction (PCR) to detect. In this case, none of the progeny resulting from an outcross of the homozygous parent carrying the trait will display the trait and extended breeding, tracking, and in some cases hybrid crosses will be required to use such a trait. This makes pirating of the technology considerably more expensive and difficult than with dominant traits. The process of making, maintaining, and providing a recessive trait requires additional steps not necessary in the production of dominant traits, and therefore requires the use of novel processes in seed and trait production.
Recessive traits that are based on optimized genes containing a specific genetic mutation may also have regulatory advantages over dominant traits made using transgenic technologies. Because such a recessive trait may not contain any newly introduced heterologous DNA, in many parts of the world it may not be regulated as a transgenic crop.